Perhaps I’ve missed it, but I would have thought that there would be a lot of discussion whether Senator Frist would have had the 50 votes he needed (together with the VP’s tie-breaking vote) for changing the filibuster rule if the agreement among the 14 senators hadn’t been reached. Stated somewhat differently, it cannot be presumed that all seven Republicans who signed the agreement would have opposed the Frist proposal if they had faced a binary choice between that proposal and doing nothing. Those of us who oppose the agreement would have far more reason to be infuriated with the Republican signatories if the agreement actually prevented 50 senators from approving the Frist proposal. Conversely, if the Frist proposal would not have passed, those who defend the agreement could argue that the agreement has produced benefits (the confirmation of Owen and, presumably, the imminent confirmations of Brown and Pryor) that would not otherwise have occurred. (Of course, this argument by defenders of the agreement would have something of a bootstrapping quality to it, since it would depend on the judgment that it was defensible for Republican senators not to support the Frist proposal.)
For what it’s worth, a very knowledgeable source assures me that Frist would have had 50 votes–specifically, that Dewine and Graham would have supported the Frist proposal if the agreement hadn’t been reached (and that no non-signatories would have jumped ship). This same source tells me that Warner, not McCain, was the real driving force in putting the agreement together.